Functional Properties And Antioxidant Activities Of Protein From Selenium-enriched Rapeseed Meal

As a byproduct of rapeseed processing, rapeseed meal contain abundant protein and fat. Rapeseed protein has similar nutritional value with soybean meal after oil extraction, as a complete protein with high quality, the biological value and use ratio are even better than that of soybean meal after oil extraction. Se possesses strong free radical scavenging activity that can protect cell and organelle membranes from oxidative damage. In the text, Se-enriched rapeseed protein isolate was prepared using the methods of alkali extraction and acid precipitation from the rapeseed meal. At the same time, the preparation conditions was optimized. Compared to the ordinary rapeseed protein, the physicochemical, functional properties, antioxidant activities, and enzymatic properties of prepared protein isolate were investigated, providing a theoretical basis for industrial utilization. The total Se in Se-enriched rapeseed meal was2times more than that in ordinary rapeseed meal, and organic Se in Se-enriched rapeseed protein isolate was up to15times more than that in ordinary rapeseed protein isolate.The amino acid patterns were found similar in Se-enriched rapeseed meal, ordinary rapeseed meal and their protein isolates, with higher levels of aspartic acid and glutamic acid, valine and threonine were the limiting amino acids, and cysteine and tyrosine were undetectable. From SDS-PAGE, both Se-enriched rapeseed protein isolate and ordinary rapeseed protein isolate mainly had two bands, with molecular size of40～65kDa and130kDa, respectively. With respect to the functional properties, the foaming and emulsifying capacity of the proteins were influenced by pH, which showed high correlation with their solubility.The results indicated that the protein of Se-enriched rapeseed possessed significantly higher antioxidant activity than that of ordinary rapeseed in all five assays. Se-enriched rapeseed protein isolate had the strongest hydroxyl radical scavenging rate.The limited enzymatic hydrolysis of Se-enriched rapeseed protein isolate by Alcalase were conducted:temperature55℃, pH8.0and E/S5%. The functional properties of the resulting hydrolysates as a function of different reaction time were discussed. The study revealed that the water holding capacity of the hydrolysates were reduced with different degree of hydrolysis, while the foaming capacity of the hydrolysates were increased compared with Se-enriched rapeseed protein isolate. Moderate hydrolysis was benefit for the oil holding capacity enhancement of Se-enriched rapeseed protein isolate. However, excessive hydrolysis had adverse effect on the oil holding and emulsifying capacity of the protein hydrolysates.